function r2_mean = model_r2_mean_1D(b,time,parameters)
nv = b(1);
sigma2 = b(2)*b(1);

mode = parameters(1);
L_0 = parameters(2)/2;

r2_mean = zeros(size(time));
for i = 1:length(time)
    r2 = 0.0;
    for n = 1:mode
        lambda = -2.0*nv*(n^2);
        temp1 = exp(lambda*time(i));
        r2 = r2+2*sigma2*(temp1-1)/(lambda);
    end
    r2_mean(i) = r2/(2*L_0);
end
end